1. Field of the Invention
The present invention relates generally to band saws and more particularly, to an emergency stop device for use in cooperation with a band saw for urging and stopping a running drive or follower wheel around which an endless band saw blade is looped.
2. Description of the Related Art
FIG. 1 shows a conventional band saw 10 comprising mainly a drive wheel 12 directly connected with an output shaft 13 of a motor (not shown in the drawing), and a follower wheel 14 driven by the drive wheel 12 through an endless band saw blade 16, which is tensionally looped around the drive wheel 12 and the follower wheel 14. When the motor is started, it will drive the drive wheel 12 to rotate, which in turn drives the band saw blade 16 to rotate the follower wheel 14. In operation, a workpiece is placed on the worktable and pushed toward an exposed cutting portion 162 of the running band saw blade 16 for cutting. Since the running cutting portion 162 is exposed to ambient environment, the band saw 10 shall be operated carefully; otherwise, severe injury may occur to the operator. For safety, the conventional band saw is always equipped with kinds of an emergency stop device.
A well-known emergency stop mechanism adopted by the conventional band saw 10 includes an emergency stop button (not shown) electrically connected with the motor for an emergency shutting down the power of the motor that drives the drive wheel 12. However, because of the law of inertia, the drive wheel 12 and the follower wheel 14, which have great mass and will gain great angular momentum when they are rotating, won't stop running immediately after the power of the motor is shut down, resulting in that the cutting motion of the band saw blade 16 will continue for a while after the motor is power-off. In light of this, it is desired to have an improved emergency stop device that can stop the cutting motion of the band saw blade immediately after the motor that drives the drive wheel is power-off.